In vehicles equipped with conventional fuel injection systems (FI systems), an ECU (electronic control unit) causes a fuel injector to inject a predetermined amount of fuel to an interior of an air-intake passage connected to an engine. In a such a fuel injection type vehicle, a tilting sensor detects that a body of the vehicle is tilted, and the ECU causes the fuel injector to stop fuel injection, thereby forcibly stopping the engine, when the tilting sensor detects that the body is tilted a specified angle or larger.
Riders often jump motocross motorcycles when traveling over bumpy mountain roads or when traveling off-road. In such circumstances, a rider may intentionally tilt a vehicle body of the motorcycle to maintain control of the posture of the motorcycle. In such a case, it is difficult for an ECU to determine whether or not to stop the engine, based only on a signal from a tilting sensor that detects that the vehicle body is tilted.
In off-road racing, for example, when the vehicle body of the motorcycle has fallen and is slightly tilted while a rider continues gripping a grip of a steering handle in a standing position, the rider may want to raise the vehicle body immediately to resume riding, without stopping the engine. In this case, it is not necessary to stop the engine, but it is difficult to determine whether or not to stop the engine only based on the signal from the tilting sensor.